Internal combustion engines include intake and exhaust valves that can be actuated by cams of at least one camshaft. In some configurations the camshafts are constructed with sliding camshaft lobes having at least one camshaft barrel. Each camshaft barrel is configured to select at least two shift positions per cylinder. The sliding camshaft lobes are rotationally locked but can move in the axial direction on a base shaft that is controlled and driven like a standard camshaft on the internal combustion engine.
At least one actuator unit is fixed on the internal combustion engine for displacing each of the sliding camshaft lobes. Particularly, at least one actuator pin of an actuator unit is operative to selectively engage displacement grooves arranged symmetrically opposite to each other on the periphery of the camshaft barrels of the sliding camshaft lobes. As the camshaft rotates, an actuator pin is selected to move into a displacement groove of the camshaft barrel which causes the sliding camshaft lobe to shift into a different axial position along the camshaft axis. When a sliding camshaft lobe shifts position, the intake and/or exhaust valves associated with it may be caused to actuate differently which in turn will cause the engine operation to be different.
To ensure the sufficient performance and reliability of engine operation it is important to know the state and position of the sliding camshaft lobes, particularly the camshaft barrels, over the full operating range of the engine. Thus, there is a need for a reliable means of determining the position of a sliding camshaft barrels at all times during engine operation.